This invention relates generally to wavelength division multiplexed optical communications systems, and more particularly to the compensation for chromatic dispersion in such systems.
With the advent of substantial new uses for electro/optic systems, there exists a greater need to effectively control the multiplexing, demultiplexing and routing of signals that are Wavelength Division Multiplexed (WDM), and Dense Wavelength Division Multiplexed (DWDM), on optical fibers. Among the operations required in managing such WDM and DWDM systems are addition of signals into empty channels (Add) and selection of signals from populated channels (Drop), split, or route signals of different channels (separate an array of input channels into even and odd channels or into bands of channels, interleaving and band channelizing), and cross connecting from m channels to n channels (m×n cross-connect).
A common and well known problem in the transmission of optical signals, present in many of the operations required in managing such WDM systems, is chromatic dispersion of the optical signal. Chromatic dispersion refers to the effect where different signals within a channel travel through a system with different spatio-temporal properties, i.e., longer wavelengths have different travel times than shorter wavelengths. When gratings are used to separate or combine the channels propagating through a system, the system design must account for the inflexibility of temporal delay functions achievable with planar gratings. These temporal delays are approximately linear (as a function of frequency) over small spectral bands, but marked nonlinearities are introduced when the spectrum of the pulse becomes broad.
In typical switched grating systems used in the operations required in managing WDM systems, not only is the chromatic dispersion significant but it varies with wavelength and is larger in the longer wavelength edge of the bands.
It is therefore an object of this invention to provide methods and systems switching/routing optical systems.
It is a further object of this invention to provide methods and systems for compensating the chromatic dispersion in twin grating disperser-combiner switchable grating optical systems.